The nature of dusty starburst galaxies in a rich cluster at z=0.4: the progenitors of lenticulars?

J. E. Geach; Ian Smail; Sean M. Moran; Tommaso Treu; Richard S. Ellis

doi:10.1088/0004-637x/691/1/783

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arXiv · 0809.4260

The nature of dusty starburst galaxies in a rich cluster at z=0.4: the progenitors of lenticulars?

J. E. Geach·Ian Smail·Sean M. Moran·Tommaso Treu·Richard S. Ellis

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Abstract

We present the results of a Spitzer Infrared Spectrograph (IRS) survey of 24um-selected luminous infrared galaxies (LIRGs, L_IR > 10^11 L_sun) in the rich cluster Cl0024+16 at z=0.4. Optically, these LIRGs resemble unremarkable spiral galaxies with e(a)/e(c) spectral classifications and [Oii]-derived star formation rates (SFRs) of <2 M_sun/yr, generally indistinguishable from the 'quiescent' star forming population in the cluster. Our IRS spectra show that the majority of the 24um-detected galaxies exhibit polycyclic aromatic hydrocarbon (PAH) emission with implied SFRs ~30-60 M_sun/yr, with only one (<10%) of the sample displaying unambiguous evidence of an active galactic nucleus in the mid-infrared. This confirms the presence of a large population of obscured starburst galaxies in distant clusters, which comprise the bulk of the star formation occurring in these environments at z~0.5. We suggest that, although several mechanisms could be at play, these dusty starbursts could be the signature of an important evolutionary transition converting gas-rich spiral galaxies in distant clusters into the passive, bulge-dominated lenticular galaxies that become increasingly abundant in the cores of rich clusters in the ~4Gyr to the present day.

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J. E. Geach, Ian Smail, Sean M. Moran, Tommaso Treu, Richard S. Ellis. 2008-09-24. The nature of dusty starburst galaxies in a rich cluster at z=0.4: the progenitors of lenticulars?. https://doi.org/10.1088/0004-637x%2F691%2F1%2F783

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